diff --git a/include/boost/json/impl/array.hpp b/include/boost/json/impl/array.hpp
index f15e10e0..275a8d50 100644
--- a/include/boost/json/impl/array.hpp
+++ b/include/boost/json/impl/array.hpp
@@ -20,7 +20,7 @@ BOOST_JSON_NS_BEGIN
 
 //----------------------------------------------------------
 
-struct alignas(alignof(value))
+struct alignas(value)
     array::table
 {
     std::uint32_t size = 0;
diff --git a/include/boost/json/impl/monotonic_resource.ipp b/include/boost/json/impl/monotonic_resource.ipp
index 5de0f3f8..d9f2d8a5 100644
--- a/include/boost/json/impl/monotonic_resource.ipp
+++ b/include/boost/json/impl/monotonic_resource.ipp
@@ -19,7 +19,7 @@
 
 BOOST_JSON_NS_BEGIN
 
-struct alignas(alignof(detail::max_align_t))
+struct alignas(detail::max_align_t)
     monotonic_resource::block : block_base
 {
 };
diff --git a/include/boost/json/impl/object.hpp b/include/boost/json/impl/object.hpp
index 00dd9cc3..f0d5acfd 100644
--- a/include/boost/json/impl/object.hpp
+++ b/include/boost/json/impl/object.hpp
@@ -20,7 +20,7 @@ BOOST_JSON_NS_BEGIN
 
 //----------------------------------------------------------
 
-struct alignas(alignof(key_value_pair))
+struct alignas(key_value_pair)
     object::table
 {
     std::uint32_t size = 0;